For many years now, scientists scour the neighbors of Earth, the Solar System and the Milky Way as they look for signs of extraterrestrial life, or other worlds that might host an advanced alien civilization. Some hunters listen to possible radio broadcasts, while astronomers and other scientists use data from the Kepler Space Telescope for finding exoplanets, or worlds that orbit other stars, in addition to rogue planets which have no host stars or systems that they can call home. The latter technique of course offers more results as scientists add more exoplanets into the list of possible habitable alien worlds.

For instance just last year, the science world was abuzz after a paper published by Tabetha Boyajian and colleagues revealed a peculiar star located more than 1,000 light-years away. This star, the KIC 8462852, or the Tabby’s star, is unlike any other. It has been gradually dimming for over a century, thus some speculate that a highly advanced alien civilization might have built a large solar energy collector near it, and it is blocking the star’s light.

So how did Boyajian’s group know that this star exists?

Scientists call it the transit method (including the Transit Photometry). They know that there’s a planet orbiting a star from light-years away when they see dimming of that star. For example, Boyajian’s group saw the KIC 8462852 dimming by 20 percent.

Apart from the KIC 8462852, scientists have found more than a thousand exoplanets by using data from the Kepler telescope.

Another good example that we should talk about is the first Earth-like exoplanet found last year orbiting at a star’s habitable zone. This planet, according to NASA, is the most Earth-like so far; it resides in the Kepler-186 system about 500 light-years from us. The American space agency said they’ll find more planets like it as they deploy more high-tech devices including the upcoming James Webb Space Telescope and the Transiting Exoplanet Survey Satellite.

With this backdrop, we can now proceed to the main topic of this article which is finding an alien world using the transit method, but not by exoplanets.

As reported by several news outlets on Wednesday, two scientists suggest that we might narrow down the hunting ground by using Earth’s so-called transit zone as it orbits the sun.

What if an intelligent alien life has been looking for other advanced worlds too using the transit method?

Published in the journal Astrobiology, scientists René Heller and Ralph Pudritz of the Max Planck Institute for Solar System Research in Canada and Germany suggest that we should start looking at possible habitable planets that could see Earth’s transit zone.

In a news release, Pudritz and Heller explain that there’s a technique called transit spectroscopy which might enable astronomers in the future to scan the atmospheres of exoplanets for indicators of life; advanced extraterrestrial life, if they exist, might use the said method to know that there’s ‘alien life’ on Earth.

“The key point of this strategy is that it confines the search area to a very small part of the sky,” says Heller from the Max Planck Institute.

Hence, Heller believes that the technique might take us less than ‘a human life span’ to find an alien civilization that might be looking for other smart species too.

“They may have detected Earth’s biogenic atmosphere and started to contact whoever is home,” he added.

And now for the result of their research: about 100,000 nearby stars could harbor worlds with extraterrestrial life “who could have discovered us and who could be trying to contact us,” they write.